1. Field of the Invention
The present invention relates to a clamping apparatus and a molding machine.
2. Description of the Art
A clamping apparatus opens and closes dies by movement of a movable die plate. The clamping apparatus imparts a clamping force to a fixed die and a movable die to clamp the dies. Various types of driving mechanisms for opening and closing the dies and for clamping the dies have been proposed.
In a clamping apparatus disclosed in Japanese Patent Publication (A) No. 2004-330552, a movable die plate is moved by screw axes in a die opening and closing direction. Ends of tie bars are fixed to pistons of clamping cylinders provided on a fixed die plate. Other ends are jointed to half nuts provided on the movable die plate. The tension is imparted to the tie bars by the clamping cylinders to generate the clamping force. There is also known a clamping apparatus used with oil pressure cylinders in place of the screw axes, disclosed in Japanese Utility Model Application No. 7-30336.
In a clamping apparatus disclosed in Japanese Patent Publication (A) No. 2004-255386, a movable die plate is movable in a die opening and closing direction by a rack provided at a base and a pinion provided at the movable die plate. A supporting plate working together with the movable die plate movable in the die opening and closing direction is provided behind the movable die plate. The supporting plate is depressed by a rod fixed to a piston of a clamping cylinder provided on the movable die plate to generate the clamping force as a result of a reaction force from the supporting plate.
The former technologies suffer from drawbacks due to the dies being opened and closed by the screw axes or the oil pressure cylinders. For example, in the screw axes, the speed of opening and closing the dies difficulty increases. In addition, in the oil pressure cylinders, since oil tanks and a lot of control valves are used, a management for preventing an oil leakage may be necessary. Therefore, a configuration and a control of the clamping apparatus can be complicated.